adminLinux Network Route and Gateway Checklist
A Linux server needs correct IP addressing, routes, gateway and DNS to communicate with the internet and private networks. A service can be healthy but unreachable if routing is wrong.
Core principle
Networking is a path problem. The server needs to know where traffic should go, and return traffic must find its way back.
Checklist
- Check IP addresses on interfaces.
- Check default route.
- Check gateway reachability.
- Check DNS resolver configuration.
- Test outbound internet access.
- Test target domain resolution.
- Check firewall rules.
- Check whether the service listens on the expected address.
- Separate local network issues from DNS issues.
- Document the network path.
Reusable lesson
This applies to VPS migrations, private networks, database separation, webhook delivery, API calls, package updates and monitoring agents.
When to Use This Checklist
Use this checklist when a Linux server cannot reach the internet, cannot resolve domains or services are unreachable despite running.
Required Tools
SSH or console access, ip, ping, dig, resolvectl, ss, firewall access, provider network information
Before You Start
Do not change remote network settings without console access or a rollback plan.
Structured Checklist Steps
- Check IP address.
- Check default route.
- Ping gateway.
- Check DNS resolver.
- Test outbound internet.
- Resolve domain.
- Check firewall.
- Check listening address.
- Separate DNS from routing.
- Document path.
Verification Steps
- Server has expected IP.
- Default route exists.
- DNS works.
- Outbound access works.
- Service reachability issue is localized.
Rollback Plan
If a route or DNS change breaks connectivity, use console access to restore the previous network configuration or switch temporarily to DHCP if safe.
Common Mistakes
- Confusing DNS failure with route failure.
- Changing IP remotely without console recovery.
- Ignoring default gateway.
- Service listening only on localhost.
- Firewall blocking expected traffic.
Related Commands
ip addr
ip route
ping -c 3 1.1.1.1
dig example.com
resolvectl status
sudo ss -tulpn
sudo ufw status numbered